Ultrasound catheter for disrupting blood vessel obstructions

ABSTRACT

Ultrasound catheter devices and methods provide enhanced disruption of blood vessel obstructions. Generally, an ultrasound catheter includes an elongate flexible catheter body with one or more lumens. An ultrasound transmission member or wire extends longitudinally through the catheter body lumen and, in many embodiments, a guide wire tube also extends through the same lumen. A distal head is fixed to or otherwise mechanically coupled with the distal end of the ultrasound transmission member or wire and is positioned adjacent the distal end of the catheter body. Although the distal end of the catheter body overlaps the distal head, the distal head is not directly affixed to the distal end of the catheter body. Thus, the distal tip may move freely, relative to the distal end of the catheter body when ultrasonic energy is applied through the ultrasound transmission member. Such a freely floating distal head enhances the efficiency of an ultrasound catheter, enabling the catheter to ablate calcific occlusions and increasing the useful life of the ultrasound transmission member and catheter.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a division of U.S. Ser. No. 10/229,371 filedAug. 26, 2002, now U.S. Pat. No. 7,137,963.

BACKGROUND OF THE INVENTION

The present invention relates generally to medical devices and methods.More specifically, the present invention relates to ultrasound catheterdevices and methods for treating occlusive intravascular lesions.

Catheters employing various types of ultrasound transmitting membershave been successfully used to ablate or otherwise disrupt obstructionsin blood vessels. Specifically, ablation of atherosclerotic plaque orthromboembolic obstructions from peripheral blood vessels such as thefemoral arteries has been particularly successful. To disrupt occlusionsof small blood vessels, such as the coronary arteries, ultrasoundcatheters must typically be sufficiently small and flexible to permittheir advancement through the tortuous vasculature of the aortic arch,coronary tree, or other similarly narrow vasculature. Thus, safely andeffectively disrupting or ablating obstructions from coronary arterieswith ultrasound energy devices depends largely on the diameter andflexibility of the ultrasound catheter employed.

Various ultrasonic catheter devices have been developed for use inablating or otherwise removing obstructive material from blood vessels.For example, U.S. Pat. Nos. 5,267,954 and 5,380,274, issued to theinventor of the present invention and hereby incorporated by reference,describe ultrasound catheter devices for removing occlusions. Otherexamples of ultrasonic ablation devices for removing obstructions fromblood vessels include those described in U.S. Pat. Nos. 3,433,226(Boyd), U.S. Pat. No. 3,823,717 (Pohlman, et al.), U.S. Pat. No.4,808,153 (Parisi), U.S. Pat. No. 4,936,281 (Stasz), U.S. Pat. No.3,565,062 (Kuris), U.S. Pat. No. 4,924,863 (Sterzer), U.S. Pat. No.4,870,953 (Don Michael, et al), and U.S. Pat. No. 4,920,954 (Alliger, etal.), as well as other patent publications W087-05739 (Cooper),W089-06515 (Bernstein, et al.), W090-0130 (Sonic Needle Corp.), EP,EP316789 (Don Michael, et al.), DE3,821,836 (Schubert) and DE2438648(Pohlman). While many ultrasound catheters have been developed, however,improvements are still being pursued.

Typically, an ultrasound catheter transmits energy from an ultrasoundtransducer through a transducer horn and then a transmission member,such as a wire, to a distal head. Ultrasound energy propagates throughthe transmission member as a sinusoidal wave to cause the distal head tovibrate. Such vibrational energy is typically utilized to ablate orotherwise disrupt vascular obstructions. To effectively reach varioussites for treatment of intravascular occlusions, such ultrasoundcatheters often have lengths of about 150 cm or longer.

One difficulty related to transmission of ultrasound energy through longcatheters is premature wear and tear and breakage of the catheter body,the ultrasound transmission member, or both. In general, an ultrasoundtransmission member or wire must be flexible enough to be passed throughvarious areas of the cardiovascular circulation, but must also havesufficient strength to transmit energy to the catheter tip to ablatevascular obstructions. A stronger, more durable transmission wire allowsfor greater transmission of energy and is more durable than a thinnerwire, but it may not be flexible or thin enough to be advanced throughthe vasculature to a desired treatment area. A thinner wire is lessdurable and more susceptible to breakage.

Currently available ultrasonic transmission wires typically break towardthe distal end of the ultrasound wire, where the cross-sectional area ofthe wire becomes smaller. Wire breakage is generally caused by stressconcentration due to transverse vibrations and fatigue. When ultrasonicenergy is conveyed through the transmission member to the distal head,the head vibrates in both a longitudinal direction (back and forth inthe direction of the longitudinal axis of the catheter) and a transversedirection (back and forth perpendicular to the longitudinal axis of thecatheter). The longitudinal vibrations typically create the beneficialeffects of disrupting an occlusion, while the transverse vibrations arepredominantly unwanted artifact that stresses and fatigues thetransmission member. One goal in developing ultrasound catheters,therefore, is to dampen transverse vibration of the transmission memberwhile still providing an optimal level of longitudinal motion.

One proposed solution for limiting transverse vibration to prevent wirebreakage in ultrasound catheters is to place one or more transversevibration absorbers near the distal end of the wire or around thesmallest cross-sectional area of the catheter, near its distal end. Sucha solution is significantly limited, however, by the structuralrequirements of an ultrasound catheter. Typically, an ultrasoundcatheter is a small, single lumen tube, which requires continuousirrigation to cool the wire while ultrasound energy is delivered.Placing one or more vibration absorbers at or near the distal endtypically increases the diameter of the catheter, interferes with thecontinuous irrigation system, or both.

Several prior patents describe such transverse vibration absorbers. Forexample, U.S. U.S. Pat. No. 5,397,293 (Alliger et al.), herebyincorporated by reference, and U.S. Pat. Nos. 5,380,274 and 5,267,954,previously incorporated herein by reference, describe catheter deviceshaving a distal head affixed to the catheter body. Affixing the head tothe catheter body acts to limit transverse motion of the head. With suchan affixed distal head, however, more ultrasound energy is required toproduce a desired amount of longitudinal vibration to disrupt or ablatea vascular occlusion. Ironically, increasing the ultrasound energyapplied to the transmission wire may actually cause increased stress onthe wire and, consequently, premature wire fatigue and breakage.

Another challenge in developing ultrasound catheters is to providesufficient mechanical energy at the distal head to break throughcalcified plaque. Intravascular plaque is often composed of calcifiedmaterial so hard that treatment devices typically cannot pass throughthem. At the present time, neither ultrasound catheters nor any othercomparable devices have solved the problem of calcific plaque occlusionsin blood vessels.

Therefore, a need exists for ultrasound catheter devices and methodsthat allow for ablation or disruption of vascular occlusions, includinghardened calcifications. Ideally, such catheter devices would besufficiently thin and flexible to be advanced through narrow, tortuousvasculature, such as the coronary vasculature, while also beingconfigured to enhance the usable life of the ultrasound transmissionwire within the catheter. Such devices would preferably providesufficient longitudinal vibration of a distal catheter head fordisrupting calcific plaque and other occlusions, while minimizing stressto the ultrasound transmission member or wire caused by transversevibration.

BRIEF SUMMARY OF THE INVENTION

Ultrasound catheter devices and methods of the present invention provideenhanced disruption of blood vessel obstructions. Generally, anultrasound catheter includes an elongate flexible catheter body with oneor more lumens. An ultrasound transmission member or wire extendslongitudinally through the catheter body lumen and, in many embodiments,a guide wire tube also extends through the same lumen. A distal head isfixed to or otherwise mechanically coupled with the distal end of theultrasound transmission member or wire and is positioned adjacent thedistal end of the catheter body. Although the distal end of the catheterbody often overlaps the distal head, the distal head is not directlyaffixed to the distal end of the catheter body. Thus, the distal tip maymove freely (or “float”), relative to the distal end of the catheterbody when ultrasonic energy is applied through the ultrasoundtransmission member.

A free-floating distal head enhances the ability of an ultrasoniccatheter to disrupt vascular occlusions by using ultrasonic energy moreefficiently. Basically, less energy is required to vibrate a floatingdistal head in a longitudinal direction for disrupting an occlusion. Byusing less ultrasonic energy, fewer unwanted transverse vibrations arecreated, thus reducing stress and fatigue of the ultrasound transmissionmember and increasing catheter longevity. The increased efficiency ofsuch a free-floating head ultrasound catheter may be used to effectivelydisrupt calcific intravascular occlusions. In many embodiments, thedistal end of the catheter body will overlap at least a portion of thedistal head, to impart stability to the free-floating head.

In one aspect of the present invention, an ultrasound catheter fordisrupting occlusions in blood vessels includes an elongate flexiblecatheter body having a proximal end, a distal end and at least onelumen. The catheter also includes an ultrasound transmission memberextending longitudinally through the lumen of the catheter body, theultrasound transmission member having a proximal end connectable to aseparate ultrasound generating device and a distal end terminatingadjacent the distal end of said catheter body. Finally, the catheterincludes a distal head coupled with the distal end of the ultrasoundtransmission member, the distal head being positioned adjacent, but notdirectly affixed to, the distal end of the catheter body. Typically, thedistal head is indirectly coupled with the catheter body, but only at alocation proximal to the distal end of the body. In some embodiments,for example, the distal head is indirectly coupled to the catheter bodyvia the guide wire tube, as described immediately below.

Optionally, the ultrasound catheter may also include a guide wire tube,having a lumen, that extends longitudinally through at least a portionof the lumen of the catheter body and extends longitudinally through thedistal head. In some embodiments, such guide wire tube is affixed to thedistal head and may also be affixed to the catheter body at a positionproximal to the distal head. In some embodiments, for example, the guidewire tube is affixed to the catheter body at a location approximately 25cm from the distal end of the catheter body. In other embodiments, theguide wire tube is affixed at a location approximately 25 cm from thedistal end and at another location within approximately 1 cm from thedistal end. Also optionally, the catheter may include a polymer sleevedisposed around a portion of the distal head, wherein the sleeve iscoupled with the guide wire tube through a small hole in the distalhead.

Generally, the distal head of the catheter may be fabricated from anysuitable material, including but not limited to a metal or a polymer. Insome embodiments, the distal head includes one or more radiopaquemarkers to improve its visibility via radiographic techniques.

Additionally, the distal head may have any suitable configuration. Insome embodiments, the tip is a bulbous member formed on the distal endof the ultrasound transmission member. In many embodiments, the distalend of the catheter body overlaps at least a portion of the distal head.For example, the distal head may include a bulbous distal portion with adiameter approximately equal to the outer diameter of the catheter bodyand which extends beyond the distal end of the catheter body, and aproximal portion having a diameter smaller than the diameter of thedistal portion, the proximal portion fitting within, but not affixed to,the distal end of the catheter body. In other embodiments, the distalhead is fully positioned within the distal end of the lumen of thecatheter body. In yet another embodiment, the distal end of the catheterbody abuts a proximal end of the distal head, the distal head having adiameter approximately equal to the outer diameter of the catheter body.

Optionally, ultrasound catheters may also include a distal sleeve,coupled with the catheter body within the lumen of the catheter body.Such a sleeve will typically comprise a hollow, cylindrical member thatsurrounds a portion of the ultrasound transmission member. The sleeveenhances stability of the catheter when the catheter is twisted ortorqued by a physician during use. For additional safety, someembodiments include an anchor member disposed within the lumen of thecatheter body. The anchor member will generally have a distal endcoupled with the distal head and a proximal end coupled with thecatheter body. In some embodiments, the anchor will comprise a wire.

The ultrasound transmission member will typically be formed of a metalalloy. In many embodiments, such metal alloy is a superelastic metalalloy. Ultrasound transmission members will often benefit from some formof cooling mechanism. Therefore, many embodiments of the invention willinclude at least one fluid outlet port located near the distal end ofthe catheter body, the fluid outlet port being in fluid communicationwith the at least one lumen of the catheter body. This will allow fluidto be injected into the proximal end of the lumen so that it may passlongitudinally through the lumen and out of the at least one fluidoutlet port. Such fluid may be used to cool the ultrasound transmissionmember.

In various embodiments, the catheter body of the ultrasound catheterwill include only one lumen, which allows passage of the ultrasoundtransmission member, a guide wire tube, and any fluids or othersubstances infused through the catheter. In other embodiments,additional lumens may be included, such as a cooling fluid lumenadjacent the ultrasound transmission member.

Generally, the ultrasound catheter apparatus will include a proximal endconnector assembly, coupled with the proximal end of the catheter body,for connecting the catheter to an ultrasound source. In one embodiment,such a connector assembly includes an elongate rigid body coupled withthe proximal end of the catheter body and having a hollow bore, thehollow bore being communicative with at least one lumen of the catheterbody, wherein the ultrasound transmission member extends proximally fromthe catheter body through at least a portion of the hollow bore. Thisembodiment of the assembly also includes one or more absorber membersdisposed within the hollow bore encircling the ultrasound transmissionmember, for absorbing transverse vibrations. The assembly also includesa sonic connector apparatus on the proximal end of the proximal endconnector assembly for connection of the ultrasound transmission memberto a separate ultrasound emitting device such that ultrasonic energy maybe transmitted through the ultrasound transmission member to the distalhead.

The proximal end connector assembly may also include one ore more fluidinlet apertures, often in the form of a Y-connector with a side-arm, forinfusing fluid through the Y-connector and into the lumen of thecatheter body. Another Y-connector side-arm may be included to allowintroduction of a guide wire into the lumen of the catheter.

In many embodiments, the ultrasound transmission member includes one ormore tapered regions near its distal end. For example, in someembodiments one or more tapered regions divide the ultrasoundtransmission member into a proximal portion and a distal portion. Inmany embodiments, the proximal portion has a larger diameter than thedistal portion. Also in many embodiments, the distal portion of theultrasound transmission member has a greater cross-sectional diameterthan the tapered region, to enhance coupling of the distal portion ofthe member to the distal head. The tapered regions of transmissionmember generally provide it with enhanced flexibility.

Optionally, the ultrasound transmission member may include a metal wirehaving a friction-reducing coating formed around it. The coating, forexample, may be composed of a polymeric material, such aspolytetrafluoroethylene or polyethylene. In other embodiments, thecoating may be comprised of a tubular jacket surrounding at least aportion of the ultrasound transmission member. In any case, the coatingor jacket may cover the entire longitudinal length or less than theentire length of the ultrasound transmission member.

In another aspect of the invention, a method for disrupting a vascularocclusion includes positioning an ultrasonic catheter device adjacentthe vascular occlusion and transmitting ultrasonic energy to the distalhead to disrupt the vascular occlusion. As described above, theultrasonic catheter device will typically include: an elongate flexiblecatheter body having a proximal end, a distal end and at least onelumen; an ultrasound transmission member extending longitudinallythrough the lumen of the catheter body, the ultrasound transmissionmember having a proximal end connectable to a separate ultrasoundgenerating device and a distal end terminating adjacent the distal endof said catheter body; and a distal head coupled with the distal end ofthe ultrasound transmission member, the distal head being positionedadjacent, but not directly affixed to, the distal end of the catheterbody.

Typically, positioning the ultrasonic catheter device will includepassing the device over a guide wire. Additionally, as described above,the method will often include infusing one or more fluids through atleast one fluid inlet aperture in the catheter body to a locationadjacent the vascular occlusion. Such infusions may be used to cool theultrasound transmission member or for any other suitable purpose.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an ultrasound catheter device andultrasound energy source according to an embodiment of the presentinvention.

FIG. 2 is a cross-sectional side view of a distal end of an ultrasoundcatheter device according to an embodiment of the present invention.

FIG. 2 a is a front view of an ultrasound catheter device as in FIG. 2.

FIG. 2 b is a partial cut-away perspective view of an ultrasoundtransmission member with a friction reducing coating or jacket accordingto an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a distal end of an ultrasoundcatheter device according to another embodiment of the presentinvention.

FIG. 4 is a cross-sectional view of a distal end of an ultrasoundcatheter device according to another embodiment of the presentinvention.

FIG. 5 is a cross-sectional view of a distal end of an ultrasoundcatheter device according to another embodiment of the presentinvention.

FIG. 6 is a cross-sectional view of a distal end of an ultrasoundcatheter device according to another embodiment of the presentinvention.

FIG. 7 is a cross-sectional view of a proximal connection assembly of anultrasound catheter device according to an embodiment of the presentinvention.

FIG. 7 a is an exploded side view of a proximal connection assembly asin FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

Ultrasound catheter devices and methods of the present inventiongenerally provide for ablation and disruption of intravascularocclusions, including calcified occlusions. An ultrasound energytransmission member, such as a wire, typically transmits energy from anultrasound transducer to a distal head of the catheter. The transmittedenergy causes the distal head to vibrate, and such vibrational energymay be used to ablate vascular occlusions. Typically, the distal head ofthe ultrasound catheter is not directly affixed to the catheter body,which allows the distal head to move freely (or “float”), relative tothe distal end of the catheter body. This freedom of movement generallyprovides increased energy transmission efficiencies, with reduced stresson the ultrasound transmission wire and, therefore, less wear and tearand premature breakage of the wire. Additionally, an unaffixed distalhead may provide greater ablative capabilities, so that calcifiedocclusions may be disrupted.

Referring now to FIG. 1, one embodiment of an over-the-wire ultrasoundcatheter apparatus 20 suitably includes an ultrasound catheter 10, aproximal end connector assembly 12 coupled with catheter 10, anultrasound transducer 14 coupled with the proximal end of proximalconnector assembly 12, and an ultrasound generator 16 with afoot-actuated on/off switch 18, which is operatively coupled withultrasound transducer 14 to provide ultrasonic energy to transducer 14and, thus, to ultrasound catheter 10. Generally, catheter 10 willinclude an ultrasound transmission member, or wire (not shown), fortransmitting energy from the transducer 14 to a distal head 26 of thecatheter.

Proximal connector assembly 12, described more fully below, may have aY-connector 15 with one or more side-arms 13, for example for providingirrigation fluid via an irrigation tube 11, or for passage of a guidewire. In other embodiments, as shown in FIG. 1, catheter 10 may bepassed along a guide wire 17 which accesses catheter 10 via a sideaperture, rather than a Y-connector side-arm.

It should be emphasized that ultrasound catheters 10 of the presentinvention may be used with any suitable proximal devices, such as anysuitable ultrasound transducer 14 or ultrasound generator 16. Therefore,exemplary FIG. 1 and any following descriptions of proximal apparatus orsystems for use with ultrasound catheters 10 should in no way beinterpreted to limit the scope of the present invention as defined inthe appended claims.

Referring now to FIG. 2, a cross-sectional side view of the distal endof one embodiment of ultrasound catheter 10 is shown. Generally,ultrasound catheter 10 suitably includes an elongate catheter body 22with at least one hollow catheter body lumen 21. In FIG. 2, catheterbody 22 is shown having one lumen, but it may have any number of lumensin various embodiments. Disposed longitudinally within catheter bodylumen 21 are an ultrasound transmission member 24 and a hollow guidewire tube 28 forming a guide wire lumen 29. Coupled with the distal endsof ultrasound transmission member 24 and guide wire tube 28 is a distalhead 26, positioned adjacent the distal end of catheter body 22.

Generally, the various coupled components described above may be coupledby any suitable means, such as adhesives, complementary threadedmembers, pressure fittings, and the like. For example, distal head 26may be coupled with ultrasound transmission member 24 and guide wiretube 28 with any suitable adhesive substance. In one embodiment, forexample, guide wire tube 28 is coupled with distal head 26 by means ofadhesive at multiple head/guide wire adhesive points 30. In someembodiments, guide wire tube 28 may also be coupled with catheter body22 by adhesive or other means at one or more body/guide wire adhesivepoints 32.

Catheter body 22 is generally a flexible, tubular, elongate member,having any suitable diameter and length for reaching a vascularocclusion for treatment. In one embodiment, for example, catheter body22 preferably has an outer diameter of between about 0.5 mm and about5.0 mm. In other embodiments, as in catheters intended for use inrelatively small vessels, catheter body 22 may have an outer diameter ofbetween about 0.25 mm and about 2.5 mm. Catheter body 22 may also haveany suitable length. As discussed briefly above, for example, someultrasound catheters have a length in the range of about 150 cm.However, any other suitable length may be used without departing fromthe scope of the present invention. Examples of catheter bodies similarto those which may be used in the present invention are described inU.S. Pat. Nos. 5,267,954 and 5,989,208, which were previouslyincorporated herein by reference.

In most embodiments, ultrasound transmission member 24, wire, or waveguide extends longitudinally through catheter body lumen 21 to transmitultrasonic energy from ultrasound transducer 14, connected to theproximal end of catheter 10, to the distal end of catheter 10.Ultrasound transmission member 24 may be formed of any material capableof effectively transmitting ultrasonic energy from ultrasound transducer14 to the distal end of catheter body 22, including but not necessarylimited to metals such as titanium or titanium or aluminum alloys.

In accordance with one aspect of the invention, all or a portion ofultrasound transmission member 24 may be formed of one or more materialswhich exhibit superelastic properties. Such material(s) shouldpreferably exhibit superelasticity consistently within the range oftemperatures normally encountered by ultrasound transmission member 24during operation of ultrasound catheter apparatus 10. Specifically, allor part of the ultrasound transmission member 24 may be formed of one ormore metal alloys known as “shape memory alloys”.

Use of supereleastic metal alloys in ultrasound transmission members isdescribed in U.S. Pat. No. 5,267,954, previously incorporated byreference. Examples of superelastic metal alloys which may be used aredescribed in detail in U.S. Pat. No. 4,665,906 (Jervis); U.S. Pat. No.4,565,589 (Harrison); U.S. Pat. No. 4,505,767 (Quin); and U.S. Pat. No.4,337,090 (Harrison). The disclosures of U.S. Pat. Nos. 4,665,906;4,565,589; 4,505,767; and 4,337,090 are expressly incorporated herein byreference insofar as they describe the compositions, properties,chemistries and behavior of specific metal alloys which are superelasticwithin the temperature range at which the ultrasound transmission memberof the present invention operates, any and all of which superelasticmetal alloys may be used to form ultrasound transmission member 24 ofthe present invention.

In many embodiments, ultrasound transmission member 24 includes one ormore tapered regions 23 along a portion of its length, towards itsdistal end. Such a tapered region 23 decreases the distal rigidity ofultrasound transmission member 24, thus amplifying ultrasound energytransmitted along ultrasound transmission member 24 to distal head 26.Tapered region 23 typically divides the transmission member 24 between aproximal portion and a distal portion, which both typically have alarger cross-sectional diameter than tapered region 23, as pictured inFIG. 2. A thicker distal portion, for example, may enhance stability ofthe connection between ultrasound transmission member 24 and distal head26. Other embodiments are contemplated, however. For example, taperedregion 23 may be positioned at the extreme distal end of transmissionmember 24. In still other embodiments, ultrasound transmission member 24may include multiple tapered portions, widened portions and/or the like.Thus, ultrasound transmission member 24 may be configured with anysuitable length, combinations of diameters and tapers, or any othersuitable shapes, sizes or configurations to advantageously transmitultrasound energy from transducer 14 to distal tip 26.

With reference now to FIG. 2 b, in some embodiments ultrasoundtransmission member 24 may include a low-friction coating or jacket 25on all or a portion of its outer surface. Coating 25 may be disposed onthe outer surface of ultrasound transmission member 24 so as tocompletely cover ultrasound transmission member 24 along its entirelength, or along a discrete region or regions thereof. Such coating orjacket 25 may comprise a layer of low friction polymer material such aspolytetrafluoroethylene (PTFE), TEFLON™ (available from Dupont, Inc.,Wilmington, Del.) or other plastic materials such as polyethylene.Coating 25 may be applied as a liquid and subsequently allowed to cureor harden on the surface of ultrasound transmission member 24.Alternatively, coating 25 may be in the form of an elongate tube,disposable over the outer surface of ultrasound transmission member 24.Generally, coating 25 serves to prevent or diminish friction between theouter surface of ultrasound transmission member 24 and the adjacentstructures of catheter 10 or proximal end connector assembly 12 throughwhich ultrasound transmission member 24 extends.

In most embodiments, distal head 26 is mounted on or otherwise coupledwith the distal end of ultrasound transmission member 24. In manyembodiments, as shown in FIG. 2, distal tip includes a proximal region27 with an outer diameter configured to fit within the distal end ofcatheter body lumen 21 and a distal region 29 with a slightly largerdiameter than proximal region 27. In many embodiments, all or a portionof distal region 29 of distal head 26 will have an outer diameterapproximately the same as the outer diameter of catheter body 22. Thus,in embodiments like the one pictured in FIG. 2, the distal end ofcatheter body 22 overlaps at least a portion of distal head 26. Theamount of overlap may vary in different embodiments, so that in someembodiments catheter body 22 may completely overlap distal head 26. Thisoverlapping may enhanced stability of the distal end of catheter 10 anddistal head 26 in particular.

In another embodiment, as shown in FIG. 3, distal head 34 is configuredso that its proximal end-abuts the distal end of catheter body 22. Inthis embodiment, distal head 26 is held in position adjacent catheterbody 22 by its attachment to ultrasound transmission member 24 and/orguide wire tube 28 and does not fit within catheter body lumen 21.Typically, in such an embodiment, all or a portion of distal head 34will have an outer diameter that is approximately equal in dimension tothe outer diameter of catheter body 22.

As is evident from distal heads 26 and 34, shown in FIGS. 2 and 3,distal heads may have any suitable configuration, shape, and sizesuitable for ablating or otherwise disrupting occlusions. For example,distal head 26, 34 may have a shape that is bulbous, conical,cylindrical, circular, rectangular or the like. Similarly, distal head26, 34 may have dimensions which allow it to fit wholly or partiallywithin the distal end of catheter body lumen 21 or may, alternatively,be disposed completely outside catheter body lumen 21. Thus, theconfiguration of distal head 26 may take any suitable form and should inno way be limited by the exemplary embodiments pictured in FIGS. 2 and 3and described above or below.

Distal head 26 is not directly affixed to the distal end of catheterbody 22. Instead, in various embodiments, it is held in place by itsattachment to either ultrasound transmission member 24, guide wire tube28, or both. In some embodiments, distal head 26 may additionally besecured to the distal end of catheter body 22 by fitting partially orwholly within catheter body lumen 21, as described above, but distalhead 26 will not be affixed to catheter body 22 with adhesive,complementary threaded members, other connective devices or the like.Thus, distal head 26 will be able to move freely, relative to the distalend of catheter body 22. Positioning distal head 26 in this way, withoutaffixing it to catheter body 22, allows greater freedom of movement ofhead 26, providing enhanced efficiency of ultrasound energy transmissionand reduced stress to ultrasound transmission member 24.

Typically, distal head 26 is actually coupled indirectly with thecatheter body at one or more points, but only at a location proximal tothe distal end of catheter body 22. In some embodiments, for example,distal head 26 is indirectly coupled to the catheter body 22 via guidewire tube 28, as described immediately below. For example, distal head26 may be coupled with guide wire tube 28, and guide wire tube 28 may becoupled with catheter body 22 at a location within 1 cm of the distalend of catheter body 22, at a location around 25 cm from the distal endof catheter body 22, or at any other location or combination oflocations. In other embodiments, distal head 26 may be coupled withultrasound transmission member 24, and ultrasound transmission member 24may be coupled with catheter body 22 near its proximal end and/or at anyother suitable location.

In some embodiments, distal head 26 is formed of radiodense material soas to be easily discernable by radiographic means. For example, distalhead 26 may be formed of a metal or metal alloy. Alternatively, distalhead 26 may be made of a polymer or ceramic material having one or moreradiodense markers affixed to or located within distal head 26. In oneembodiment, for example, distal head 26 may be molded of plastic such asacrylonitrile-butadiene-styrene (ABS) and one or more metallic foilstrips or other radiopaque markers may be affixed to such plastic distalhead 26 in order to impart sufficient radiodensity to permit distal head26 to be readily located by radiographic means. Additionally, inembodiments wherein distal tip 26 is formed of molded plastic or othernon-metallic material, a quantity of radiodense filler such as powderedbismuth or BaSO₄ may be disposed within the plastic or othernon-metallic material of which distal head 26 is formed so as to impartenhanced radiodensity to distal head 26.

Typically, guide wire tube 28 will also be disposed longitudinallywithin catheter body lumen 21, along all or a portion of the luminallength. In most embodiments, guide wire tube 28 will also extend throughdistal head 26, as shown in FIGS. 2 and 3. It should be understood,however, that guide wire tube 28 and guide wire lumen 29 may be givenany suitable configuration, length, diameter and the like suitable forpassing catheter 10 along a guide wire to a location for treatment. Forexample, in some embodiments, a relatively short guide wire lumen 29 maybe formed near the distal end of catheter body 22 to permit rapidexchange of guide wires and catheters. In some embodiments, guide wirelumen 29 may be accessed via a side-arm 13 on a Y-connector 15, while inother embodiments guide wire lumen 29 may be accessed via a guide wireaperture in a side wall of catheter body 22. Thus, catheters 10 of thepresent invention are not limited to those including guide wire tubes 28and or guide wire lumens 29 as described by FIGS. 2 and 3.

In many embodiments, guide wire tube 28 is attached to both distal head26 and catheter body 22. As previously described, such attachment may beaccomplished by any suitable means, such as by an adhesive substance.Generally, guide wire tube 28 is attached within a portion of distalhead 26 at one or more adhesive points 30. An outer wall of guide wiretube 28 also may be attached to an inner wall of catheter body 22 at oneor more guide wire tube/catheter body adhesive points 32. For example,in some embodiments tube/catheter body adhesive point 32 is locatedapproximately 25 cm from the distal end of catheter body 22. Otherembodiments may include one tube/catheter body adhesive point atapproximately 25 cm from the distal end of catheter body 22 and anothertube/catheter body adhesive point within approximately 1 cm of thedistal end of catheter body 22. Any suitable adhesive point orcombination of multiple adhesive points is contemplated.

Such attachment of guide wire tube 28 to both distal head 26 andcatheter body 22 helps to hold distal head 26 in its position at thedistal end of catheter body 22. Attachment also helps limit unwantedtransverse motion of distal head 26 while allowing longitudinal motiondue to tube elasticity. Adhesives used to attach guide wire tube 28 todistal head 26 and catheter body 22 may include, but are not limited tocyanoacrylate (eg. Loctite™, Loctite Corp., Ontario, CANADA. or DronAlpha™, Borden, Inc., Columbus, Ohio) or polyurethane (e.g. Dymax™,Dymax Engineering Adhesive, Torrington, Conn.) adhesives.

In still other embodiments, a portion of distal head 26 may be formed toextend laterally wider than the outer surface of catheter body 22 andguide wire tube 28 may be positioned on the outer surface of catheterbody 22. Such embodiments, wherein guide wire tube 28 is positionedalong the outer surface of catheter body 22, are commonly referred to as“monorail” catheters, as opposed to “over-the-wire” catheters asdescribed by FIGS. 2 and 3. In addition to over-the-wire embodiments andmonorail embodiments, ultrasound catheter 10 may also be configured as acombination or hybrid of over-the-wire and monorail embodiments.Specifically, such embodiments may include an ultrasound catheter 10having a guide wire tube 28 formed through a distal portion of catheterbody 22 only, with a guide wire entry/re-entry aperture being formedthrough a sidewall of catheter body 22 to permit passage of a guide wirefrom the distal guide wire lumen of the catheter to a position outsidethe catheter body.

With reference now to FIG. 2 a, some embodiments of ultrasound catheter10 include one or more fluid outflow apertures 36 in distal head 26 topermit fluid flow out of catheter body lumen 21. Other embodiments (notshown) may include one or more similar apertures at or near the distalend of catheter body 22, either in addition to or in place of apertures36 in distal head 26. Outflow apertures 26 facilitate continual orintermittent passage of coolant liquid through lumen 21, for example byinfusion into lumen 21 via one or more side-arms 11, 13. Infusion ofcoolant liquid through lumen 21, in proximity to ultrasound transmissionmember 24, may be used to control the temperature of ultrasoundtransmission member 24 to prevent overheating during use. Coolingliquids may include, but are not limited to, saline and the like.

In some embodiments, guide wire tube 28 and lumen 29 are generallyconfigured with an inner diameter slightly larger than the outerdiameter of a guide wire along which catheter 10 is passed. Such a guidewire tube 28 may then be used as an alternative or additional means toallow fluid outflow through distal head 26. In still other embodiments,one or more separate lumens having separate outflow apertures formed ator near the distal tip of the catheter may be formed for infusion ofoxygenated perfusate, medicaments or other fluids into the blood vesselor other anatomical structure in which the catheter is positioned.

Referring now to FIG. 4, some embodiments of ultrasound catheter 10include a distal sleeve 72 which is coupled with catheter body 22 andwhich surrounds a portion of ultrasound transmission member 24.Generally, distal sleeve 72 comprises a hollow cylindrical member, madeof any suitable material, such as but not limited to a polymer. Sleeve72 is coupled with catheter body 22 within lumen 21 at a location nearthe distal end of catheter body 22. Sleeve 72 may be coupled with body22 via any reasonable means but will often by coupled via an adhesive atone or more adhesive points 74, such as those described above forcoupling other components of catheter 10.

By surrounding a portion of ultrasound transmission member 24 and beingcoupled with catheter body 22, distal sleeve 72 adds stability tocatheter 10. Although it is not necessary for use of catheter 10 anddoes not enhance the performance of catheter 10, physicians often twistor torque catheters radially upon insertion and/or during use of acatheter. Such twisting motions may cause guide wire tube 28 to kinkand/or collapse as the tube 28 moves in relation to catheter body 22 andtransmission member 24. Placement of distal sleeve 72 aroundtransmission member 24 causes the components of catheter 10 to movetogether when catheter 10 is twisted, thus avoiding kinking orcollapsing of guide wire tube 28 and maintaining patency of guide wirelumen 29.

Referring now to FIG. 5, another embodiment of ultrasound catheter 10includes a distal head sheath 82. Distal head sheath 82 is generally acylindrical sheath that surrounds a portion of distal head 26. Sheath 82is coupled with guide wire tube 28 via an adhesive at an adhesive point84, which is accessed through a small hole 86 in a side portion ofdistal head 26. Sheath 82 may be made of any suitable material, but willtypically be made of a polymer of the same or similar material withwhich guide wire tube 28 is made. Securing sheath 82 to tube 28 throughhole 86 in distal head 26, enhances the stability of the connectionbetween tube 28 and distal head 26. Thus, there is less chance thatdistal head 26 will break off from catheter 10 and safety of the deviceis enhanced. Forming sheath 82 and guide wire tube 28 from the same orsimilar materials will allow for a secure connection between the two viaan adhesive.

With reference now to FIG. 6, yet another embodiment of catheter 10includes a distal head anchor 94. Distal head anchor 94 may comprise awire or similar device made from metal, polymer or any other suitablematerial. Generally, a distal portion of anchor 94 is coupled withdistal head 26 at an adhesive point 96, and a proximal portion of anchor94 is coupled with catheter body 22 at an adhesive point 92 proximal tothe extreme distal end of catheter body 22. Therefore, distal head 26remains free-floating relative to the extreme distal end of catheterbody 22 but is anchored to catheter body 22 at a more proximal location92. This anchoring helps ensure that distal head 26 will not break offfrom catheter 10 during use. Any suitable anchoring device may be usedand is contemplated within the scope of the invention.

Various types and designs of proximal end connector apparatus 12,ultrasound transducers 14, ultrasound generation devices 16 and/or thelike may be coupled with ultrasound catheter 10 for use of catheter 10to disrupt vascular occlusions. Detailed descriptions of such apparatusmay be found, for example, in U.S. Pat. Nos. 5,267,954 and 5,380,274,invented by the inventor of the present invention and previouslyincorporated herein by reference. Therefore, the ultrasound cathetersapparatus 20 and methods are not limited to use with any particulartransducers 14, ultrasound generators 16, connector apparatus 12 or thelike.

That being said, and with reference now to FIG. 7, one embodiment ofproximal end connector apparatus 12 suitably includes a housing 42 witha hollow inner bore 44. Bore 44 may have a uniform inner diameter alongits length or, alternatively, may have multiple segments, such as aproximal segment 47, a middle segment 45 and a distal segment 49, eachof which may surround one or more various components of proximal endconnector apparatus 12.

Generally, proximal segment 47 of bore 44 is configured to allowattachment to ultrasound transducer 56, via transducer housing 58 andtransducer thread 54. As such, proximal segment 47 includes a proximalportion of sonic connector 48, including a sonic connector thread 52 forconnection with complementary transducer thread 54. Proximal segment 47and/or the proximal end 41 of housing 42 may have any shape, diameter orconfiguration to allow coupling with transducer housing 58. As shown inFIG. 7, proximal segment 47 may have an inner diameter of a size toallow transducer housing 58 to fit within it. Thus, transducer housing58 and proximal end 41 may be coupled via a pressure fit. In otherembodiments, transducer housing 58 and proximal end 41 may connect viacomplementary threads. In still other embodiments, transducer housing 58may fit around the outer diameter of proximal end 41. It should beapparent that any suitable configuration of proximal end may be used.

Similarly, sonic connector thread 52 may have any suitable size, shapeand configuration for coupling with a complementary transducer thread54. Such coupling may be achieved via complementary threads, snap-fitmechanism, or any other suitable means. Otherwise, sonic connectorthread 52 and sonic connector 48 are generally configured to transmitultrasound energy from ultrasound transducer 56 to ultrasoundtransmission member 24. A pin 50 is generally positioned within sonicconnector 48 and is disposed between proximal segment 47 and middlesegment 45 of bore 44.

Middle segment 45 of bore 44 typically surrounds a portion of sonicconnector 48, which is coupled with the distal end of ultrasoundtransmission member 24, and one or more sets of absorber members 46,which surround a portion of ultrasound transmission member 24 to reducevibration of member 24. Absorber members 46 may include, for example,one or more O-rings. Sonic connector 48 is coupled with the distal endof ultrasound transmission member 24 by any suitable means, to transmitultrasound energy to member 24 from transducer 56.

Absorber members 46 are configured to circumferentially surroundultrasound transmission member 24 in whole or in part to dampentransverse vibrations created by the transmission of ultrasound energy.The number, size and configuration of absorber members 46 used may bedetermined based upon a desired level of dampening and any suitableconfiguration or combination may be used. Alternatively, other dampeningstructures may be used, rather than absorber members 46, and thus theconfiguration of proximal connector apparatus 12 is not limited to theuse of one or more sets of absorber members 46.

Distal segment 49 of bore 44 typically surrounds a portion of ultrasoundtransmission member 24 and may also contain one or more additional setsof absorber members 46. Distal segment 49 may also contain a portion ofa Y-connector 15, which is coupled with the distal end 43 of housing 42of proximal end connector apparatus 12. Again, coupling of Y-connector15 with distal end 43 of apparatus 12 may be accomplished viacomplementary threads, pressure fitting, or any other suitable means. AY-connector lumen 45 of Y-connector 15 allows passage of ultrasoundtransmission member 24 and is in communication with catheter body lumen21.

Y-connector 15 may have one or more side-arms 11 to allow passage of aguide wire, infusion of a cooling fluid or any other suitable fluid, orpassage of any other suitable structure or substance from side-arm 11,through Y-connector 15, to catheter 10. In some embodiments, a lumen ofside-arm 11 is in fluid communication with Y-connector main lumen 45 andcatheter body lumen 21. In other embodiments, side-arm 11 may have alumen that communicates with a separate lumen in Y-connector 15 andcatheter body 22.

Generally, pressurized fluid such as a coolant liquid may be infusedthrough side-arm 11, through Y-connector lumen 45 and through catheterbody lumen 21 so that it flows out of fluid outflow apertures 36. Thetemperature and flow rate of such coolant liquid may be specificallycontrolled to maintain the temperature of ultrasound transmission member24 at a desired temperature within its optimal working range. Inparticular, in embodiments of the invention wherein ultrasoundtransmission member 24 is formed of a metal alloy which exhibits optimalphysical properties (e.g. super elasticity) within a specific range oftemperatures, the temperature and flow rate of coolant liquid infusedthrough fluid infusion side-arm 11 may be specifically controlled tomaintain the temperature of ultrasound transmission member 24 within arange of temperatures at which it demonstrates its most desirablephysical properties. For example, in embodiments of the inventionwherein ultrasound transmission member 24 is formed of a shape memoryalloy which exhibits super elasticity when in its martensite state, butwhich loses super elasticity as it transitions to an austenite state, itwill be desirable to adjust the temperature and flow rate of the coolantliquid infused through fluid infusion side-arm 11 so as to maintain theshape memory alloy of ultrasound transmission member 24 within atemperature range at which the alloy will remain in its martensite stateand will not transition to an austenite state. The temperature at whichsuch shape memory alloys transition from a martensite state to anaustenite state is known as the “martensite transition temperature” ofthe material. Thus, in these embodiments, the fluid infused throughside-arm 11 will be at such temperature, and will be infused at suchrate, as to maintain the shape memory alloy of ultrasound transmissionmember 24 below its martensite transition temperature.

Referring now to FIG. 7 a, proximal end connector apparatus 12 is shownin exploded side view. In this embodiment, sonic connector 48 is heldwithin housing 42, by means of dowel pin 50. In other embodiments, dowelpin 50 may not be included and sonic connector 48 may be positionedwithin housing by other means. Otherwise, FIG. 4 a simply demonstratesthe various components previously described with reference to FIG. 4.

Although the invention has been described above with specific referenceto various embodiments and examples, it should be understood thatvarious additions, modifications, deletions and alterations may be madeto such embodiments without departing from the spirit or scope of theinvention. Accordingly, it is intended that all reasonably foreseeableadditions, deletions, alterations and modifications be included withinthe scope of the invention as defined in the following claims.

1. A method for disrupting a vascular occlusion in a blood vessel, themethod comprising: positioning an ultrasonic catheter at a locationwithin the blood vessel near the occlusion, wherein the ultrasoniccatheter comprises: an elongate catheter body having at least one hollowlumen and a distal end; an ultrasound transmission member disposed atleast partially within the hollow lumen of the elongate catheter body; adistal head coupled with a distal end of the ultrasound transmissionmember, the distal head comprising at least one fluid outflow aperture;and a hollow guidewire tube having a guidewire lumen, wherein the hollowguidewire tube is coupled with the distal head and an outer wall of theguidewire tube is attached to an inner wall of the catheter body at anadhesive point; engaging the distal head of the catheter against theocclusion, wherein the distal head is disposed adjacent the distal endof the catheter body but is not directly affixed to the distal end ofthe catheter body; infusing fluid through the at least one fluid outflowaperture in the distal head to a location adjacent the vascularocclusion; and vibrating the distal head while engaged against theocclusion to disrupt the occlusion.
 2. A method as in claim 1, whereinthe step of positioning the distal end includes passing the hollowguidewire tube over a guide wire.
 3. A method as in claim 1, wherein thestep of vibrating the distal head includes transmitting energy to causethe distal head to vibrate with a frequency of between 20 kHz and 40kHz.
 4. A method as in claim 1, further including infusing fluid throughat least one fluid outflow aperture in the elongate catheter body of theultrasonic catheter to a location adjacent the occlusion.